The described subject matter relates generally to aircraft landing gears, and more specifically to steering systems for aircraft landing gears.
Landing gear for large aircraft have traditionally employed a telescoping shock-absorbing strut with a multi-wheel truck attached. Such structures can effectively handle and react the various forces seen during taxiing. In order to assist in turning the aircraft, reduce side loads acting upon landing gear during turns, and reduce tire scrubbing, main landing gears with six wheeled or greater bogie beam configurations have utilized a steerable aft and/or forward axle. Most common approaches to provide for axle steering utilizing hydraulic actuators that directly or indirectly push or pull the axle to the desired steering angle. Traditional push-pull steering systems are sized to produce enough steering torque at the minimum moment arm. As a result, the available steering torque is higher than required for most of the steerable range.
To alleviate certain issues with false steering angle feedback in push-pull actuated steering mechanisms, a system was developed by which an actuator is mounted transversely to a bogie beam, with steering movement transferred from the actuator to the axle via a rack-and-pinion arrangement. While effective for its intended purpose, the rack-and-pinion gears require more frequent maintenance as compared to a push-pull steering system due to oxidation and infiltration of contaminants into the gear teeth.